Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$109.35	3.309%	$112.9684	$112.97	$112.95	$113.00
Purchase #2	$237.96	7.275%	$255.2716	$255.27	$255.25	$255.30
Purchase #3	$59.73	10.260%	$65.8583	$65.86	$65.85	$65.90
Purchase #4	$160.88	5.247%	$169.3214	$169.32	$169.30	$169.30
Purchase #5	$111.35	10.695%	$123.2589	$123.26	$123.25	$123.30
Purchase #6	$204.54	8.705%	$222.3452	$222.35	$222.35	$222.30
Purchase #7	$126.98	10.683%	$140.5453	$140.55	$140.55	$140.50
7 purchase totals =	$1,010.79		$1,089.5691	$1,089.58	$1,089.50	$1,089.60